This invention relates to improvements in an oil separator provided in combination with a cylinder head cover of an internal combustion engine to separate oil mist in blow-by gas to be discharged out of the engine through the cylinder head cover.
As is well known, in an internal combustion engine of an automotive vehicle, blow-by gas containing unburnt gas component leaked into a crankcase from combustion chambers of the engine is again introduced or recirculated into the combustion chambers through an engine air intake system, together with fresh taken in from the outside of the engine. In such recirculation of blow-by gas, blow-by gas flowing through the crankcase contains oil mist of lubricating oil. In order to prevent oil mist from being carried to the engine intake system, in general, an oil separator is provided in combination of a cylinder head cover as a single unit so that the blow-by gas is taken out from the engine after oil mist is separated from blow-by gas by the oil separator, as disclosed in Japanese Patent Provisional Publication Nos. 2000-45750 and 7-243317. In general, two blow-by gas paths are connected to the cylinder head cover, in which fresh air is introduced through one of the two blow-by gas paths under a normal engine operating condition while blow-by gas flows through both the two blow-by gas paths under a high engine load operating condition. The cylinder head cover is provided with two oil separators which are respectively used for the two blow-by gas paths.
Many oil separators provided in combination with the cylinder head cover have been proposed. In an arrangement of Patent Provisional Publication No. 2000-45750, an inner plate having a plurality of small holes for oil separation is horizontally disposed, in which blow-by gas passed through the small holes strike against projection portions formed at a ceiling surface. Accordingly, oil droplets separated are spread on the upper surface of the inner plate thereby clogging the small holes. This lowers an oil separation performance of the oil separator.
In the arrangement of Patent Provisional Publication No. 7-243317, a cover-like inlet member is disposed at the bottom plane of an inlet opening which is open to the upper side of a camshaft in order to prevent oil droplets raised up by the camshaft from directly entering the inlet opening. This inlet member increases the whole height of the cylinder head cover by an amount corresponding to the inlet member.